Usage at [[\yii\base\Model::behaviors()]] add the following code
~~~
return [
...
[
'class' => 'mdm\upload\UploadBehavior',
'uploadPath' => '@common/upload', // default to '@runtime/upload'
'attribute' => 'file', // attribute use to receive from FileField
'savedAttribute' => 'file_id', // attribute use to receive id of file
],
];
~~~